Glow-discharge valve



Jan. 24, 1928.

v "1,656,957 F. SCHROTER GLOW DISCHARGE VALVE Filed March 1921 smnmoPOTENTIAL.

2&0

i I Z I 3 I 3 "M1 Peacam'ma o: HYDROGEN ADMIXED TO THE RARE, 0A8

W'ilnessasr. I Inventor.-

Fmrz .Sc/m'ra? y jittorneys Patented Jan. 24,192s.

TION or NEW xoax.

Application med Iarch so, 1921, Serial no.

The present invention relates to improvements in discharge tubes, whichcontain rare gases or rare gas mixtures, such, for instance, as helium,neon, argon and the like,

' under a reduced pressure, and in which a so-called glow-dischargetakes place on a non-incandescent cathode, the main portion of thevoltage consumption occurring in the Crookes dark space. The inventionhas for its object to facilitate the starting of such tubes in lightingand power circuits of ordinary voltage (for instance, 110 to 220 volts),and to produce tubes working safely and having a long life, so that theyare capable of serving as rectifiers for alternating currents, forchoking strong voltages and similar purposes. v When I refer to thechoking of strong voltages I have in mind cases in which the tube isconnected in series with one or more weak current apparatuses, which,owing to the choking efi'ectof the tube, receive reduced voltage fromthe lighting or power supplying circuit. In the following it is supposedthat in all tubes of this kind the distance of the electrodes from oneanother is so small that they are capable of being started with as low avoltage as possible.

The invention starts from the recognition of the fact that in glowdischarge tubes of the kind mentioned, after a short time of use, therare gas charge may attain a state of very high purity, which resultsfrom the large area of the cathode to be used in order to obtainsufiiciently strong discharge cur rents. This is in turn due to theocclusion of all gaseous impurities, such, for instance, as hydrocarbon,hydrogen, nitrogen and the like, originally present in the rare gas. Now

49 the effect of this automatic purification of the rare gas by means ofthe discharge is a strong increase of the starting potential of thetube. It may reach so high a figure tliat finally the tube can no longerbe rendered active by the supplying current voltages em- 10 ed. p I willhereafter explain my invention with reference to the accompanyingdrawing in which it is diagrammatically illustrated, and

50 showing, what occurs if a small amount of hydrogen is fed to thetubewhich is filled with a mixture of neon and helium under a pressure(vacuum) of 10 m/m. mercury, and

GLOW-DISCHARGE VALVE.

urrz scimo'rn'a, or nnmm-sonuanenmaomr, GERMANY, ASSIGNOR, BY mm: Al-

SIGNMENTS, 'ro AMERICAN TELEPHONE am) TELEGRAPH COMPANY, A

456,984, and in Germany January 23, 1918. I

in which the anode consists of a pointed iron w1re 1 and is placedwithin a large-surface llOIl sheet metal tube 2 at a distance of about15 ni/m. from the tube walls. The concen- CORI'ORA- tration of thehydrogen is shown in percentages of the total quantity as abscissae andthe starting potential in volts as ordinates. The shape of the curve,which shows the dependency of the starting potential upon theconcentration of the hydrogen, can be indicated only approximately inthe neighborhood of the ordinate axis, since the voltage also depends onthe quality of the surface of the electrode substance used. Neverthelessthe curve shows pretty well the approx mate shape of the startingpotential. It Wlll be seen that, as soon as the hydrogen contentsapproach zero, the starting potentlal increases considerably and finallysurpasses the voltage values at disposal on the supplying circuit. Likeconditions exist when additional gases other than hydrogen, and likewisemetal vapours are used. It will be noted that the cathode 2 is aso-called cold cathode, as distinguished from filamentarycathodes heatedby the passage of a current from an external source, as used in certainother types of vacuum tubes. The action in tubeshaving such heated orincandescent cathodes is materially different from that occurring with acold cathode such as used in my invention.

Now the invention consists in that in low discharge tubes of the kindspecified suc an amount of a suitable activating gaseous agent such asone or more chemically reactive gases or vapors, as, for instance,hydrogen, nitrogen, or gases acting in a similar manner is admixed tothe rare gas that occlusion will not cause the whole amount of theadmixed gas to disap ear so that consequently the rare gas withm thetube cannot be in a pure state. In case the cathode of the tube consistsof iron, nickel, copper, tungsten or a like metal, difficult ofvolatilization, hydrogen, nitrogen, gaseous carbonaceous compounds,phosphorus vapors are especially suitable'as chemically reactive gases,and, as metal vapors, mercury or volatile metal compounds are mainlyused. Hydrogen especially is used advantageousl in a concentration offrom 1 to 3%. T e concentration is selected in accordance with the sizeof the alectrod their location in relation to each other, an thepotential of the current vto be used. A portion of the hydrogen admixedis absorbed by the electrodes, but at the ratio indicated a certain partalways re mains effective in a free state.

If strongly electrofipsitive substances, such, for instances, as aalinemetal or substances containing alkaline metal, are used for thecathode, hydrogen and nitrogen have pmven particularly suitable. It istrue, 'these gases are entirely absorbed b the cathode surface as longas the disc large p through the tube, but after the discharge has beeninterrupted, traces of the same are again freed; therefore, for carryingthe invention into effect it is sufiicient to use alkaline metalscontaining hydrogen or nitrogen. As long'as no current passes throughthe tube such metals always give ofi to the gas filling very smallquantities of hydrogen or nitro n, which are effective in the mannerdescri For carryi out the invention it is not nry to 5min the additionalgases to the rare gusprior to admitting the same to the discharge tube.Such admixtures to the rare gas ma also be effected by using theelectrode an co in a porous state and allowing it to remain in touchwith the additional gas or va or for some time, so that it absorbs a sucient quantity of the same. In some cases it has proved sufiicient tofree electrodes or other inner parts of the tube onl partially fromgaseous impurities when e austing the same.

The additional gases mentioned not only secure in tubes of the kind as sified the starting with the voltage of ordinary lighting or powersupplying circuits but at the same time they retard the disintegrationof the cathode and thereby ensure an increased life of the tubes.

vessel containing argon under reduced pressure mixed with hydro en.

In testimony whereo I have aflixed my signature.

FRITZ sonnornn

